The present invention relates to a method of checking wrapping material in a packaging machine.
In particular, the invention relates to wrapping material of the type decoiled from a roll and fed to a processing station in the form of a continuous strip, or of discrete lengths separated previously at a cutting station, also to wrapping material procured in the form of blanks taken from a stack.
It is normal for such materials, before entering a first station of a machine where they are wrapped around the respective products being packaged, to undergo an operation in which accessory materials are applied to selected areas.
Depending on the particular requirements, these accessory materials can take the form of adhesives, inks, and metallic powders utilized for example in combination with adhesive substances.
In accordance with conventional techniques, the accessory materials in question must be applied to selected areas of the wrapping material and can be distributed in different ways. They can appear for example as spots, or as continuous or discontinuous stripes, or in other specific patterns.
Clearly, the distribution of accessory materials in this manner must be repeated cyclically on each length of wrapping material destined to provide a single wrapper, and similarly, the geometry of the distribution must remain identical for each such length.
If this is not the case, the steps of wrapping and packaging the finished product could give rise to structural or visual defects necessitating the rejection of the substandard products at a point downstream of the wrapping stations.
The object of the present invention is to provide a method of checking wrapping materials, generally considered, whereby the correct distribution of accessory materials can be verified upstream of the wrapping stations and the above noted problems duly overcome.